Genetic Genealogy

 

Genetic genealogy is the use of DNA to determine family relationships

Here is a very plain English description of how DNA helps predict family relationships as I am using it to reconstruct our Highland Bains. 

DNA is inherited strictly as 50% from our father and 50% from our mother. However, the 50% that either parent gave to us is only about 25% of what they inherited from their parents, ie our grandparents. That approximation is because autosomal DNA is scrambled in a random way during recombination of chromosomes.  Recombination occurs every time an egg and a sperm cell merge to form a new person. Recombination is why we are different in so many ways from our siblings. This is how Ancestry illustrate random recombination, with more detail in the link at the bottom of the page.


In generational terms, the approximate proportion of intact DNA sequences we inherit from our ancestors is listed below. Descendants of our grandparents are our first cousins and there is 100% chance of matching them. We will match on a large number of segments, and some of these segments will have come from Buchan ancestors. Descendants of our x2 great grandparents are our third cousins, and there is only a 10% chance that we will not match them on any DNA, including Bain DNA. [Note that these figures are changing on a regular basis].

Chances of inheriting particular DNA

Ancestor                                                     Cousinship                      Chance of DNA match*

grandparents - 25%                                      First                                    100%

x1 great-grandparents - 12.5%                    Second                                100%

x2 great grandparents - 6.25%                    Third                                    90%

x3 great grandparents - 3.125%                   Fourth                                 46% 

x4 great grandparents - 1.56%                     Fifth                                    10%

x5 great grandparents - 0.78%                     Sixth                                   <2%


As Alexander Bain and Margaret Chisholm are my x4 great grandparents, the chances of me having any of their DNA inside me is only about 1.5%. I will match very few people descended from their other children who are my 5th cousins, only 10% of the time. Luckily I do match several such cousins, one described in Fodderty - Alexander's siblings and DNA.

See the following resources to help understand this critically important scientific method.

Ancestry post

Diahan Southard particularly her blog posts on understanding matches

Cousin statistics

Comments

Post a Comment

Popular posts from this blog

Our part of the Highlands

Image
Margaret Bain was born on 10 May 1833 at Highfield, Ross-shire. So says her baptismal record and so says her passenger records of her emigration to the Australian colonies, which was confirmation that the Margaret on the Mary Pleasants was the right one! It is time to discover the places and times of Ross-shire in the Highlands of Scotland.  The Highlands of Scotland are a world apart from the lowlands, where Robert Buchan was born in 1834. See later posts for information about their different language, history, culture and industries. In essence the Highlands is an area of northern Scotland defined by its geographical isolation. It is heavily mountainous, with people surviving on its coasts, and along its glens that pierce the mountains often enough. The Great Glen is a remarkable location on a map of Scotland, extending from Inverness in the east to Fort William in the west. Formed by a geological fault that has the norther part of Scotland moving in a different different directi...
Read more

Chisholm or Chisolm - who?

Image
Margaret Chisholm, our Bain matriarch, enters our story in 1796, when she married one of the Alexander Bains. They married in Dingwall, with the only clue being that her father was the late Don Chisolm "or Millan".  There is only one Margaret whose father was called Don born in Ross-shire on ScotlandsPeople.  This child was born in 1785 in Kiltearn, so she is is too young to marry in 1796. I have found only one Margaret born on the border of Ross-shire and Inverness-shire whose father was Donald.  She was born on 1 January 1780 in the parish of Kiltarlity, and baptised on 11 January. This girl's parents were Don Chisholm and Margaret Cameron . Is she the right Margaret? How can we possibly know? One approach is to wonder how likely it is that a girl born in Inverness-shire married a man in Dingwall in Ross-shire? Firstly it is worth realising that Dingwall was the county town of Ross-shire and therefore a place where people might travel to for work, or have contacts in so...
Read more

Finding stuff on this blog

Image
Posts on the "Our Highland Bains" blog are either about people, places or researches. DNA is included in researches. Click on any hyperlink below to go directly to that post. Leave a comment to get in touch. People Margaret Bain goes to Australia - bringing Bains to Australia Alexander and Catherine [Matheson] - Margaret's parents Margaret's siblings in Scotland - five stayed Margaret Chisholm - our new matriarch   Alexander and Margaret [Chisholm] - our earliest generation to date The Matheson Clan The Bain Clan Margaret Bain about 40 years old, Australia Places Fodderty: Exploring the area in 2025 - a guided tour The Statistical accounts - the Old in 1790s and the New in 1840s Fodderty Cemetery  Dingwall: The Statistical Accounts - the Old in1790s and the New in1840s The Highlands of Scotland Our part of the Highlands - where we came from Researches [including DNA] Key DNA matches - early finds of an early generation
Read more